Adaptation of Monolithic Crowns Produced by Four CAD-CAM Systems

Objectives: This in vitro study evaluates the marginal adaptation and internal fit of monolithic lithium disilicate crowns produced by four different CAD-CAM systems.
Methods: CAD-CAM systems were selected: Ceramill (Ceramill Motion 2), Cerec (Cerec 3), EDG (CAM5-S1 SmartDent) and Zirkonzahn (M5 Heavy). An artificial lower first molar was prepared for a full crown, duplicated in plaster, scanned and the crown was designed following standardized parameters. Ten lithium disilicate crowns (IPS e.max CAD) per group were milled. The crowns were filled with low viscosity silicone and seated on the prepared tooth. The pellicle formed was scanned by the SkyScan 1076 micro-CT system and subsequently embedded in heavy body silicone, sectioned and captured by means of a stereomicroscope at 50x magnification, according to replica technique. Internal and marginal adaptation were measured in the micro-CT and in stereomicroscope images. Data were submited to two-way ANOVA followed by Tukey’s test (α=.05) and Pearson's correlation coefficient was performed to evaluate the correlation between methods.
Results: Marginal adaptation presented values ranging from 48,2 ± 19,6 µm to 133,0 ± 71,5 µm. Highest averages were found for the axial (170,1 ± 38,2 µm Zirkonzahn group/micro-CT) and occlusal (229,4 ± 49,0 µm Cerec group/micro-CT) areas. Pearson's correlation coefficient was performed to compare the two methods of adaptation analysis and it was statistically significant, showing a strong correlation between the methods (p= 0,01 and r=0,69).

Conclusions: The four tested CAD-CAM systems were able to produce monolithic lithium disilicate crowns with clinically acceptable levels of marginal adaptation and internal fit.